1. Field of the Invention
This invention relates to hollow fibers which are light, and which have a favorable hand with both a dry and bulky feel, as well as a manufacturing method thereof. In particular, the present invention relates to porous hollow fibers having a preferable cross section like a lotus root, and a fiber structure thereof.
2. Discussion of the Background
Synthetic fibers such as polyester and polyamide are generally used in clothing as well as industrial applications because of their excellent physical and chemical properties, and are industrially and commercially valuable. However, compared with natural fibers such as silk, cotton and linen, synthetic fibers have monotonous hand or gloss, because of a simple distribution of yarn fineness, large yarn fineness and simple transverse cross sectional shape. Furthermore, synthetic fibers are typically low in quality and have a cold and slimy feel. In order to improve the above-described synthetic fibers and address these drawbacks, a profiled transverse cross sectional shape synthetic fibers is adopted, or the structure of the fibers is made hollow.
Typically, however, fibers having a profiled cross section, or hollow fibers manufactured by using profiled or hollow spinning nozzles are problematic in that the profiled cross section is lost, or the hollow portions tend to collapse either by the surface tension of the resin in a molten state from spinning to solidification or by the take-up tension during spinning. In particular, when developing a porous hollow shape, even when the fibers have a porous hollow structure just after spinning, the porous hollow portion collapses and is eliminated or the proportion of the hollow portion tends to decrease, so that it has been substantially impossible to obtain fibers with porous hollow portions by the above methods.
Japanese Published Unexamined Patent Application No. Hei 7-316977 proposes a technique of forming conjugate fibers using an alkali-decomposable polymer as an island component and an alkali-resistant polymer with water absorption rate of 3% or more, such as polyamide or ethylene vinyl alcohol type copolymer as a sea component, and removing the decomposable polymer with a hot aqueous alkali solution to obtain porous hollow fibers. This technique undesirably requires a difficult treatment of the waste water that contains the alkali-decomposed products and leaves significant environmental problems. In addition, since it is necessary to extract the island component with aqueous alkali solution through the sea component of the conjugate fibers, the method restricts the type of the polymer in that a water absorbing polymer must be used for the sea component. It is difficult to use a polylactic acid or polyester sensitive to alkalis for the sea component, and it is substantially impossible to produce porous hollow fibers wherein the sea component includes polyesters mainly composed of polylactic acid, polyethylene terephthalate or polybutylene terephthalate as the skeleton.
It is an object of the present invention to solve the foregoing problems associated with the conventional fibers.
It is another object of the present invention to provide hollow fibers constituted with a so-called hydrophobic polymer scarcely showing water absorption.
It is another object of the present invention to provide hollow fibers having a porous hollow portion excellent in lightness, dry and bulky feels, as well as a fiber structure containing them.
It is another object of the present invention to provide conjugate fibers suitable for the manufacture of hollow fibers without waste water treatment problems or environmental problems.
This invention further intends to provide a method of manufacturing hollow fibers using such conjugate fibers.
These and other objects may be accomplished with the present invention, the first embodiment of which provides a hollow fiber, which includes:
at least one thermoplastic polymer with an equilibrium water content of 2% or less;
wherein the number of hollow portions (xcex11) and a hollow ratio (xcex12) in said fiber satisfy the following equations:
xcex11xe2x89xa77
2xe2x89xa6xcex12xe2x89xa665
xe2x80x830.14xe2x89xa6(xcex11xc3x97xcex12)/100xe2x89xa6250.
Another embodiment of the present invention provides a fiber structure, which includes the hollow fiber as described above.
Another embodiment of the present invention provides an article selected from the group including multi-filament yarn, spun yarn, woven fabric, knitted fabric, non-woven fabric, paper, artificial leather, fiberfill, textured yarn, blended filament yarn, blended spun yarn, twisted yarn, entangled yarn, crimped yarn, union woven fabric, union knitted fabric, fiber laminate, natural fiber laminate, semi-synthetic fiber laminate, synthetic fiber laminate, clothing, living material, industrial material, medical articles, and combinations thereof, which includes the hollow fiber as described above.
Another embodiment of the present invention provides a method for making hollow fibers, which includes:
treating with water at least one sea-island conjugate fiber that includes:
a sea component that includes at least one thermoplastic polymer with an equilibrium water content of 2% or less; and
an island component that includes at least one water soluble thermoplastic polyvinyl alcohol polymer; wherein
the number of island components (xcex1n) and the island component ratio (xcex1s) in the conjugate fiber satisfy the following equations:
xcex1nxe2x89xa77
2xe2x89xa6xcex1sxe2x89xa665
0.14xe2x89xa6(xcex1nxc3x97xcex1s)/100xe2x89xa6250;
and dissolving to remove the water soluble thermoplastic polyvinyl alcohol polymer from the conjugate fiber;
to prepare a hollow fiber.
Another embodiment of the present invention provides a hollow fiber, produced by the process described above.
Another embodiment of the present invention provides a method of treating a fiber structure, which includes:
treating with water a fiber structure that includes at least one sea-island conjugate fiber, wherein the sea-island conjugate fiber includes:
a sea component that includes at least one thermoplastic polymer with an equilibrium water content of 2% or less; and
an island component that includes at least one water soluble thermoplastic polyvinyl alcohol polymer; wherein
the number of island components (xcex1n) and the island component ratio (xcex1s) in the conjugate fiber satisfy the following equations:
xcex1nxe2x89xa77
2xe2x89xa6xcex1sxe2x89xa665
0.14xe2x89xa6(xcex1nxc3x97xcex1s)/100xe2x89xa6250;
xe2x80x83and dissolving to remove the water soluble thermoplastic polyvinyl alcohol polymer from the conjugate fiber.
Another embodiment of the present invention provides a sea-island conjugate fiber, which includes:
a sea component that includes at least one thermoplastic polymer with an equilibrium water content of 2% or less; and
an island component that includes at least one water soluble thermoplastic polyvinyl alcohol polymer; wherein the number of island components (xcex1n) and the island component ratio (xcex1s) in the conjugate fiber satisfy the following equations:
xcex1nxe2x89xa77
2xe2x89xa6xcex1sxe2x89xa665
0.14xe2x89xa6(xcex1nxc3x97xcex1s)/100xe2x89xa6250.